Biphenyl degradation by Paenibacillus sp. PRNK-6: follows a characteristic lower metabolic pathway
Nagarathna S.V., Chandramouli Swamy T.M., Pooja V. Reddy and Anand S. Nayak*
Department of Biochemistry, Gulbarga University, Kalaburagi-585106 {India} *Corresponding author Dr. Anand S. Nayak Professor Department of Biochemistry Gulbarga University, Kalaburagi-585106 {India} anandsnayak@gmail.com* +91 9448441952
ABSTRACT
The metabolic pathwayinvolved in the assimilation of biphenyl in the facultative anaerobic bacterium Paenibacillus SP. PRNK-6 was studied, as the sole carbon source at an optimized concentration of 400 mgL-1. The strain utilized 90.42% of biphenyl within 72 hours of incubation. The assimilation of biphenyl in the PRNK-6 strain began with the initiation of di-oxygenation, leading to the formation of cis-2,3- dihydro-2,3-dihydroxybiphenyl, which by undergoing dehydrogenation forms 2,3-dihydroxybiphenyl. The di-hydroxybiphenyl further upon ring cleavage at the meta position forms benzoic acid and 2-hydroxy-6-oxo- 6-phenylhexa-2,4-dienoate. Further benzoic acid undergoes hydroxylation to give 4-hydroxybenzoic acid; a current novel metabolite of the study. The 4-hydroxybenzoic acid upon further hydroxylation and subsequent degradation of protocatechuate and catechol was obtained, as characterized by analyzing the metabolites using HPLC and GC-MS. A probable metabolic route was postulated by identifying metabolites using GC-MS and HPLC, the growth on pathway intermediates, and the specific activity of key enzymes.